1. Field of the Invention
This invention relates to a method for fabricating and to the resulting apparatus for implementing a unique semiconductor optical filter sensor that is suitable for providing accurate representations of a physical parameter in an optical sensor system.
2. Prior Art
Conventional sensors which are adapted to measure various physical characteristics of a sample, typically provide an analog electric output signal. Such conventional analog sensors may be limited in some applications because of their relatively large size. Moreover, systems that have heretofore been interfaced with sensors of the prior art are relatively expensive to fabricate, are often not capable of carrying sufficiently wide bandwidth signals, and lack immunity to electromagnetic and/or electrostatic interference.
Devices that are known to those skilled in the art and which are generally adapted to optically convey information that is transmitted by means of incident light beams to measure various physical parameters (such as temperature, pressure, etc.) operate in a manner involving a plurality of reflections and splittings of a single beam of incident light so that interference and support of the components of the incident light may occur numerous times. Therefore these devices have the disadvantageous characteristic of intensity variations that are inimical to the accuracy of the signal representation of the sensed parameter.
An example of an optical sensor that is interfaced with a fiber optic transmission system to provide accurate digital representations of a physical parameter from a remote sample can be found in U.S. patent application Ser. No. 928,223 entitled "FIBER OPTIC TEMPERATURE SENSOR", filed July 26, 1978. However, nothing is known in the prior art which shows or suggests the claimed method and resulting apparatus for utilizing a semiconductor material that has optical-wavelength-dependent filter characteristics that may be varied as a function of a physical parameter such as temperature. Furthermore, nothing is known in the prior art which applies amorphous semiconductor material in an optical filter for any purpose, let alone for use in an apparatus for sensing physical parameters, such as that disclosed and claimed below.